Experiments and simulations demonstrating the rapid ultrasonic rewarming of frozen beef cryovials

TL;DR

This study demonstrates that ultrasonic rewarming significantly accelerates the thawing of frozen biological samples, achieving up to 2.5 times faster rates than thermal conduction alone, with potential benefits for tissue viability.

Contribution

The paper introduces a novel ultrasonic rewarming method using a 444 kHz transducer, supported by experiments and simulations showing enhanced rewarming rates for cryopreserved samples.

Findings

Ultrasound increased rewarming rates tenfold compared to conduction.

Maximum rewarming rate of 57°C/min achieved with ultrasound.

Simulations aligned well with experimental results, showing uniform heating.

Abstract

The development of methods to safely rewarm large volume cryopreserved biological samples remains a barrier to the widespread adoption of cryopreservation. Here, experiments and simulations were performed to demonstrate that ultrasound can increase rewarming rates relative to thermal conduction alone. An ultrasonic rewarming setup based on a custom 444 kHz tubular piezoelectric transducer was designed, characterized, and tested with 2 mL cryovials filled with frozen ground beef. Rewarming rates were characterized in the -20$^{\circ}$C to 5$^{\circ}$C range. Thermal conduction-based rewarming was compared to thermal conduction plus ultrasonic rewarming, demonstrating a ten-fold increase in rewarming rate when ultrasound was applied. The maximum recorded rewarming rate with ultrasound was 57$^{\circ}$C per minute, approximately 2.5 times faster than with thermal conduction alone. Coupled acoustic and thermal simulations were developed and showed good agreement with the heating rates demonstrated experimentally and were also used to demonstrate spatial heating distributions with small ($<$3$^{\circ}$C) temperature differentials throughout the sample when the sample was below 0$^{\circ}$C. The experiments and simulations performed in this work demonstrate the potential for ultrasound as a rewarming method for cryopreserved tissues, as faster rewarming rates may improve the viability of cryopreserved tissues and reduce the time needed for cells to regain normal function.